Nothing to do with WP. Ignorant customer reps are everywhere.
You do know O2 have got a beta going on a datasense app don't you?
I'm well aware yes. I have the beta for '(the Lab) My O2 Live Tiles' (what a mouthful). But let's be clear, it's not a DataSense app. Right now, the Live Tiles app plugs into your mobile phone account profile and pulls down a subset of basic allowance usage, information easily obtainable on the MyO2 website. That's fine but DataSense is much more than that. DataSense allows you to inspect how much data specific apps are using over cellular data and Wifi. You can set limits on data usage and it compresses web pages via a proxy to conserve your data allowance. It also can automatically switch to carrier sponsored Wifi hotspots when available.
there aren't any other UK carriers offering the service either.
Vodafone UK supports DataSense.